Re: Compaq presario F756NR CD/DVD rom not working or even showing in device manager.

It's a problem with the motherboard related to the well known video chip solder joints. In 2006 they started using lead free solder and it has failed from heat on many laptops made after 2006 creating many problems such as dvd drives not being recognized and wireless cards not working. When it completely fails the video goes dead and the laptop won't boot anymore.

The fix it to get the video chip reflowed or replace the motherboard. Sometimes you get lucky and installing a copper shim between the heatsink and the video chip will fix it but it is not guaranteed to work forever. Hope this helps.